Following The University of Texas at Austin’s campus-wide evacuation this morning, UT president Bill Powers explained how his law enforcement and communications teams handled the challenge to public safety—the response to a telephoned bomb threat.

UT’s crisis management team, Powers said, then worked with other agencies at the state and federal levels to determine the threat’s credibility. The decision to evacuate all campus buildings was made at 9:30 a.m., and an emergency text went out to nearly 69,000 subscribers shortly thereafter.

“It got to the point where the prudent thing was to clear all buildings,” Powers explained at a noon press conference.”We couldn’t assure ourselves that this was not a credible threat.”

Powers said the caller didn’t specify anything would occur exactly at 90 minutes, but instead could potentially occur after that timeframe.

He added that the evacuation was intended to clear buildings, not the entire Forty Acres. “We were just getting students out of the buildings,” he said. “We weren’t trying to get the students off of the campus.”